The invention relates to the field of training devices and simulators, and, more specifically, to training in the use and wearing of a supplemental air supply apparatus that involves a face mask and inflatable air bags.
Emergency situations are best handled by personnel skilled in competent procedures that have been acquired through experience and training. The best insurance is good preparation.
Many emergencies require that the responding personnel be provided breathing apparatus to cope with toxic environments. Fires, chemical leaks, explosive atmospheres and underground operations are obvious critical environments where breathing assistance is needed. In such cases the operator must be confident in the apparatus and his own ability to operate it safely and effectively. Otherwise, his attention to the task at hand will suffer in the emergency.
For perfect realism, the apparatus itself would be used in training. But, inasmuch as operational containers of oxygen and oxygen generating devices are used with oxygen breathing apparatuses, cost becomes a significant factor when the operational apparatus is employed for training.
Therefore, simulation is encouraged. Accordingly, the next best thing to the perfect realism of the aparatus itself is the apparatus, slightly modified for training. That is what the present invention provides, with an insignificant loss of realism.
Oxygen breathing apparatuses (OBA's) for the most part are closed loop systems which are not vented except by a relief valve. Other apparatuses have filtering arrangements that often include chemical bags for removing a substantial segment of the irritants from the air. In both cases, an inflatable breathing bag may be used. And, it is to simulators having an inflatable breathing bag that the present invention is directed. The simulators for training on the use of the OBA's is the application for which the present invention was originated; however, the techniques disclosed and claimed have application to simulated filtering apparatuses as well that have inflatable bags.
The prior art includes earlier work by the present inventor, such as the oxygen breathing apparatus breathing bag simulator/trainer that is described in the Navy Technical Disclosure Bulletin, Volume 10, No. 1, of Sept. 1984, wherein a modification kit is disclosed that emulates inflation of the operational OBA bag by redirecting exhaled air into supplemental bags that are removably attached in covering relationship to the back of the operational bags. A filter canister is substituted for the OBA's oxygen generator and repiped directly to the user's facemask to couple outside air through the filter to the user. A relief valve is included in the supplemental bags to vent the exhaled air to the outside and prevent over-pressurization. In the operational OBA's the oxygenated air that is on its way to the user first is used to build pressure in the bags and inflate them, whereas the above-described simulator uses air after it has been exhaled by the user to inflate the bags. Another simulator by the inventor that uses exhaled air to inflate the bags is described in U.S. Pat. No. 4,265,238. Therein an operational OBA is disclosed as prior art and shown to include a flexible tube within each bag that provides a circuitous air path from the oxygen generator through one tube emptying into its bag, and from the first bag to the second bag and into its tube which is coupled at its other end to the user's facemask. The other side of the facemask is coupled to the oxygen generator to complete the closed system and recharge the air that is exhaled by the user. The invention is a modification to the operational OBA that converts it to a simulator, and substitutes a flow-through canister for the oxygen generator and adds a crossover valve near the facemask. The crossover valve reverses the air path within the bags such that exhaled air is used to inflate the bags, whereas inhaled air comes directly through the canister to the facemask. Excess pressure within the bags is vented to the outside by a relief port within the crossover valve.
Simulation has been without some necessary effects, however. One is what results from an accidental deflation of the bags. With the operational equipment, bumping or impact to one or both of the bags can cause the bag to lose its air. When the bag deflates there is no air available to the facemask, and the inexperienced user initially develops a feeling of panic. Heretofore, simulation and training has not provided the trainee with that experience. Inasmuch as the bag is inflated with exhaled air in the simulator, loss of inflation does not remove the source of oxygen from the facemask. The result is a potential for negative training. What has been needed is a modification to the simulator that will temporarily inhibit comfortable breathing when the simulator's breathing bag has been accidentally deflated.
Apparatus that automatically shuts off the supply of gas when pressurization is lost in the system is shown in the prior art by the respirator of U.S. Pat. No. 4,364,384 that uses a combination of mechanical triggers operating in close tolerance to permit the systematic use of a measured amount of oxygen but prevent the unlimited venting of oxygen to the outside when the facemask is removed from the user. The system distinguishes between normal inhalation-exhalation and complete depressurization by first and second levers connected to first and second valves, respectively. The first valve opens when normal inhalation has permitted the bag to be deflated its designed amount and come into contact with the first lever; and, the second valve closes when the bag is deflated beyond the designed amount and comes into contact with the second lever. The latter occurs when the otherwise closed system, is opened by a rupture in the system or removal of the facemask. A similar system, but without the automatic shut-off feature, is shown by U.S. Pat. No. 4,195,627 that has a separate valve for each of its two canisters. The user's exhaled air passes through the oxygen generator canister first until the breathing bag is partially inflated, then simultaneously through both canisters until the bag is substantially inflated, and finally only through the carbon dioxide filter canister to full inflation. The valves are operated by a chain that is connected to the far wall of the bag. As the bag is inflated the chain becomes taut and begins to open the valve from the filter while it begins to close the valve from the generator.
Accordingly, none of the known prior art has provided for a training device that simulates the loss of available air to the user of an oxygen breathing apparatus of the type employed by emergency personnel, such as is caused by the unexpected collapse of at least one of the OBA's air bags.